Conventional Diesel engines commonly operate at lower maximum revolutions per minute than comparable gasoline engines. One reason is that the droplets of fuel injected at the end of a compression stroke mix slowly with the available oxygen, and this causes slower combustion than in a comparable gasoline engine where the air and fuel are premixed. In addition, unless there is more air than needed for stoichiometry, combustion in a Diesel engine will be incomplete and carbon particles will be exhausted as black smoke. Techniques to overcome these problems and to improve engine performance are described in the literature (see, for example, U.S. Pat. Nos. 3,353,520, 3,911,890, 3,977,376, 4,044,740, and 4,096,697).